LABORATORY REPORT
CHM478 – PRINCIPLE OF PHYSICAL CHEMISTRY
NAME / STUDENT ID
Chirsty Renang / 2024203274
PROGRAMME CODE /
Bachelor in Science (Chemistry) with
GROUP
Honours(AS242) / AS2422A
EXPERIMENT
Experiment 3 – Factors Affecting Rate of Reaction
Date of experiment
: 24/04/2025
Date of submission
: 5/05/2025
Name of lecturer
: NORHASNAN BIN SAHARI
1
INTRODUCTION :
The rate of a chemical reaction refers to how fast reactants are converted into
products. Understanding the factors that influence reaction rates is essential in both industrial
and laboratory settings, where controlling reaction speed can affect efficiency, safety, and
outcome. This experiment aimed to investigate three key factors that affect the rate of
reaction: concentration of reactants, temperature, and the presence of a catalyst.
In Part A, the effect of concentration was studied using potassium iodide and
hydrogen peroxide, where the time taken for a blue-black colour to appear (indicating the
formation of iodine-starch complex) was measured at different concentrations.
H2O2 + 2I- + 2H+ → 2H2O + I2
I2 + 2S2O32- → 2I- + S4O62In Part B, the effect of temperature on reaction rate was investigated using
potassium permanganate and oxalic acid, with the rate assessed by the time taken for the
purple colour of permanganate to disappear. In Part C, the role of a catalyst was examined by
repeating the same reaction from Part B, this time with the addition of manganese sulfate as a
catalyst.
In general, rate of reaction can be measured using:
Rate (Ms-1) =
𝛥 [ 𝑝𝑟𝑜𝑑𝑢𝑐𝑡 𝑜𝑟 𝑟𝑒𝑎𝑐𝑡𝑎𝑛𝑡 ]
𝛥 𝑡𝑖𝑚𝑒 (𝑠)
These experiments demonstrate how changes in concentration, temperature, and
the presence of a catalyst can significantly alter the speed of chemical reactions, supporting
fundamental principles in chemical kinetics.
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OBJECTIVE :
To study the factors of concentration, temperature and catalyst on rates of reaction.
CHEMICAL AND APPARATUS :
Stopwatch
0.1M hydrogen peroxide
Hotwater bath
0.1M potassium iodide
Boiling tubes
2.0M sulphuric acid
Measuring cylinder
0.01M potassium permanganate
Dropper
0.5M oxalic acid
Beaker
0.1M manganese sulphate
Conical flask
0.005M sodium thiosulphate
Starch solution
Distilled water
METHODS/PROCEDURE:
PART A: EFFECT OF CONCENTRATION
1. 10 cm³ of potassium iodide (KI) and 10 cm³ of sulfuric acid (H₂SO₄) were measured
and transferred into a conical flask. Then, 10 cm³ of sodium thiosulphate (Na₂S₂O₃)
and 3 drops of starch solution were added.
2. 10 cm³ of hydrogen peroxide (H₂O₂) was measured and quickly transferred into the
conical flask containing the KI, H₂SO₄, Na₂S₂O₃, and starch. The mixture was swirled
and the stopwatch was immediately started. The stopwatch was stopped as soon as the
blue-black colour appeared. The time taken for the appearance of the blue-black
colour was recorded.
3. Steps 1 and 2 were repeated using 2 cm³, 4 cm³, 6 cm³, and 8 cm³ of distilled water,
added into the conical flask containing KI. The total volume of the mixture was kept
at 30 cm³. The experiment was repeated accordingly.
PART B: EFFECT OF TEMPERATURE
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1. 3 cm³ of potassium permanganate (KMnO₄) and 3 cm³ of sulfuric acid (H₂SO₄) were
measured and transferred into a clean boiling tube.
2. 3 cm³ of oxalic acid was transferred into another boiling tube and then quickly added
into the boiling tube containing the KMnO₄ and H₂SO₄ mixture. The boiling tube was
stoppered and shaken. The stopwatch was started immediately. The time taken for the
dark purple colour of KMnO₄ to disappear was recorded.
3. Steps 1 and 2 were repeated at different temperatures (40°C, 50°C, and 60°C). Before
mixing, the boiling tube containing the KMnO₄ and H₂SO₄ mixture was placed in a
hot water bath until the desired temperature was reached. The solutions were then
mixed and the reaction was carried out as before.
PART C: EFFECT OF THE PRESENCE OF CATALYST
1. Steps 1 and 2 in Part B were repeated, but this time 3 drops of manganese sulfate
(MnSO₄) solution were added to the test tube before mixing. This step was conducted
at room temperature.
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RESULT & DATA ANALYSIS :
Room temperature (°C) : 25 °C
Exp
A
1
2
3
4
5
KI
(ml)
10
8
6
4
2
H2O
(ml)
0
2
4
6
8
Reaction Mixture
Conical flask
H2SO4
Na2S2O3
(ml)
(ml)
10
10
10
10
10
10
10
10
10
10
Test tube 1
B
1
2
3
4
KMnO4
(ml)
3
3
3
3
H2SO4
(ml)
3
3
3
3
Test
tube 2
H2C2O4
(ml)
3
3
3
3
1
KMnO4
(ml)
3
H2SO4
(ml)
3
Rate of
reaction
(Ms-1)
20
15.3
10.5
8.7
6.4
0.040
0.065
0.095
0.115
0.156
Temperature (°C)
Time
(s)
Rate of
reaction
(Ms-1)
Room temperature
40
50
60
30.03
29.0
28.0
27.0
0.033
0.034
0.036
0.037
Starch
(drops)
3
3
3
3
3
Test tube 2
Temperature (°C)
Test tube 1
C
Time
(s)
MnSO4
(ml)
3
H2C2O4 (ml)
3
QUESTIONS AND DISCUSSION
2.Calculate concentration of KI (M) used in part A.
Answer:
Use: C1V1=C2V2
(0.1M)×(10) = C2×(30)
C2=
0.1×10
30
= 0.0333 M
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Beaker
H2O2
(ml)
10
10
10
10
10
Time
(s)
Rate of
reaction
(Ms-1)
110s
0.909
3.Calculate the rate of reaction for each of the experiment in part a, part b and part c
Answer:
Rate of Reaction=
1
Time taken (s)
Part A
A
Time (s)
1
20
2
Rate of reaction (Ms-1)
Rate of Reaction=
15.3
3
Rate of Reaction=
8.7
5
1
15.3s
1
10.5s
Rate of Reaction=
6.4
= 0.040 Ms-1
24.80s
Rate of Reaction=
10.5
4
1
Rate of Reaction=
1
8.7s
1
6.4s
= 0.065 Ms-1
= 0.095 Ms-1
= 0.115 Ms-1
= 0.156 Ms-1
Part B
B
Time (s)
1
30.03
2
3
4
29.0
28.0
27.0
Rate of reaction (Ms-1)
Rate of Reaction=
Rate of Reaction=
Rate of Reaction=
Rate of Reaction=
1
30.03s
1
29.0s
1
28.0s
1
27.0s
= 0.033 Ms-1
= 0.034 Ms-1
= 0.036 Ms-1
= 0.037 Ms-1
Part C
C
Time (s)
1
110s
Rate of reaction (Ms-1)
Rate of Reaction=
6
1
1.10s
= 0.909 Ms-1
4. Discuss in term of molecular collision theory on the effects of changes in
concentration of KI, temperature and the presence of catalyst on the rate of reaction.
Answer:
According to molecular collision theory, a chemical reaction occurs when reactant particles
collide with enough energy (called activation energy) and proper orientation. The rate of
reaction depends on the frequency and effectiveness of these collisions.
In part A,when the concentration of potassium iodide (KI) increases, the number of iodide
ions in the solution also increases. This leads to a higher frequency of collisions between
reactant particles, increasing the chances of successful collisions per unit time, and thus, the
rate of reaction increases.
For part B,the increase in temperature provides more kinetic energy to the reactant particles.
As a result, particles move faster and collide more frequently. More importantly, a greater
proportion of the particles have energy equal to or greater than the activation energy, making
collisions more effective. Therefore, increasing the temperature significantly increases the
rate of reaction.
Lastly, in part C the presence of a catalyst such as manganese sulfate (MnSO₄) provides an
alternative reaction pathway with a lower activation energy. This means more collisions have
enough energy to result in a reaction, even at the same temperature. Although the catalyst
does not increase the frequency of collisions, it increases the proportion of successful
collisions, which speeds up the reaction.
So overall, increasing concentration and temperature raises the rate of reaction by increasing
the number or energy of effective collisions, while a catalyst increases the rate by lowering
the energy barrier for those collisions.
5. An appropriate illustration( eg:Maxwell Boltzmann and energy profile diagram) shall
be included to support the explanation.
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DISCUSSION :
In Part A, increasing the concentration of potassium iodide (KI) led to a faster
appearance of the blue-black colour. This is because a higher concentration increases the
number of reactant particles in a given volume, resulting in more frequent collisions.
Consequently, the likelihood of effective collisions—those with sufficient energy and proper
orientation—increases, thus speeding up the reaction.
In Part B, the rate of reaction increased with rising temperature. At higher
temperatures, particles gain kinetic energy and move faster, leading to more frequent and
energetic collisions. A greater proportion of particles have energy equal to or greater than the
activation energy, increasing the number of successful collisions. This trend was clearly
observed as the time for the purple colour of potassium permanganate to disappear decreased
with increasing temperature.
In Part C, the addition of manganese sulfate (MnSO₄) as a catalyst resulted in a
faster reaction rate compared to the uncatalyzed reaction in Part B. The catalyst provided an
alternative reaction pathway with lower activation energy, allowing more particles to
successfully react even without increasing temperature. This supports the concept that
catalysts increase reaction rate without being consumed in the reaction. Overall, the results
confirmed that higher concentration, higher temperature, and the presence of a catalyst all
contribute to increasing the rate of reaction. The trends observed were consistent with
theoretical expectations based on collision theory and energy profile considerations.
One possible source of error is inaccurate timing due to delays in starting or
stopping the stopwatch, which may affect the measured reaction time. This can be minimized
by using digital timing tools or conducting multiple trials and averaging the results. Another
source of error is uneven mixing of reactants, which may result in inconsistent reaction rates;
this can be reduced by standardizing the swirling method and mixing duration.
In Part B, temperature fluctuations during the transfer of solutions from the water
bath could affect the reaction rate. To minimize this, the solution temperature should be
confirmed with a thermometer before mixing, and all glassware should be pre-warmed. Using
impure or expired chemicals may also affect the outcome, so it's important to use fresh,
uncontaminated reagents. Lastly, inaccurate volume measurements could alter
concentrations; using calibrated measuring equipment and reading volumes at eye level helps
ensure precision.
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CONCLUSION :
The experiment successfully demonstrated that the rate of a chemical reaction is
affected by concentration, temperature, and the presence of a catalyst. Increasing the
concentration of potassium iodide and the temperature both resulted in faster reactions due to
more frequent and energetic particle collisions. The use of a catalyst, manganese sulfate, also
increased the reaction rate by lowering the activation energy. These findings support the
principles of collision theory and chemical kinetics, confirming that these three factors play
significant roles in influencing reaction speed.
REFERENCES :
1. Chang, R., & Goldsby, K. A. (2016). Chemistry (12th ed.). McGraw-Hill Education.
Petrucci, R. H., Herring, F. G., Madura, J. D., & Bissonnette, C. (2017). General chemistry:
Principles and modern applications (11th ed.). Pearson Education.
2. Tro, N. J. (2020). Chemistry: A molecular approach (5th ed.). Pearson Education.
3. Zumdahl, S. S., & DeCoste, D. J. (2020). Introductory chemistry: A foundation (9th
ed.). Cengage Learning.
4. Royal Society of Chemistry. (n.d.). Rates of reaction: The effect of concentration and
temperature. Retrieved from https://edu.rsc.org
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